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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The possible role of the renin-angiotensin system in the maintenance of hypertension in two-kidney, one clip hypertensive rats was studied. Plasma renin activity rose rapidly and markedly in association with the elevation of blood pressure and then decreased gradually, although blood pressure remained high. Renin activity in the lung, aorta, and mesenteric artery also increased with the development of hypertension and then decreased in a way similar to that of plasma renin activity at the chronic stage of hypertension. Plasma angiotensin converting enzyme activity did not change significantly until 16 weeks after unilateral renal artery clipping, whereas vascular angiotensin converting enzyme activity significantly increased at the chronic, but not the acute, stage of hypertension. In chronically renal hypertensive rats, 1-sarcosine, 8-isoleucine angiotensin II or enalapril, an angiotensin converting enzyme inhibitor, lowered the blood pressure and enalapril also lowered the angiotensin converting enzyme activity of vascular tissues. The constrictor effect of angiotensin I was greater in isolated arteries from chronically hypertensive rats than in those from age-matched normotensive rats. These results suggest that the vascular renin-angiotensin system plays an important role in the maintenance of two-kidney, one clip hypertension. Elevated vascular angiotensin converting enzyme activity appears to increase local production of angiotensin II, which results in vasoconstriction by acting directly and indirectly through adrenergic nerves on vascular smooth muscle.
Hypertension 1986 Jul
PMID:Vascular renin-angiotensin system in two-kidney, one clip hypertensive rats. 301 74

We examined the time course and extent to which central and peripheral mechanisms contribute to the short-term effects of a 500-mg oral dose of alpha-methyldopa on supine mean arterial pressure, cardiac output, and total peripheral resistance, as well as its effects on total urinary excretion of norepinephrine and its metabolites, in five subjects with essential hypertension. Total peripheral resistance was reduced significantly 1 hour after alpha-methyldopa administration and remained so for the ensuing 7 hours of the study (p less than 0.05). A small but significant reduction in mean arterial pressure occurred 7 hours after the dose (p less than 0.05), while cardiac output did not change significantly. Total 24-hour urinary norepinephrine and metabolite excretion was reduced by 8.1 mumol (35% compared with placebo). The relative distribution of urinary norepinephrine metabolites was unaffected by alpha-methyldopa, and the catecholamine metabolites of alpha-methyldopa, alpha-methylnorepinephrine and alpha-methylnormetanephrine did not account for this reduction. Competitive inhibition of methyldopa transport across the blood-brain barrier and into the central nervous system by large oral doses of isoleucine antagonized most of the effect of alpha-methyldopa. The effects on total peripheral resistance were completely abolished, and small, insignificant changes during the 7-hour study were similar to those observed after placebo. Changes in mean arterial pressure were not significant; however, 24-hour total urinary norepinephrine and metabolite excretion increased by 6.1 mumol to 22.7 mumol (24.7 mumol excreted after placebo). Adding benserazide to the alpha/methyldopa-isoleucine dose regimen in an attempt to inhibit any residual, presumably peripheral, effects of alpha-methyldopa caused little, if any, further antagonism.(ABSTRACT TRUNCATED AT 250 WORDS)
Hypertension 1986 Jan
PMID:Evidence for a predominantly central hypotensive effect of alpha-methyldopa in humans. 394 83

Two angiotensin II analogues (AIIA), 1-sarcosine, 8-isoleucine angiotensin II ([Sar, Ile]-AII) and 1-sarcosine, 8-alanine angiotensin II ([Sar, Ala]-AII), were infused in six normal volunteers on high, regular and low sodium diets. The agonist and antagonist activities of these AIIA on blood pressure (BP), plasma aldosterone concentration (PAC), creatinine clearance and plasma renin activity were examined. Both AIIA had agonistic pressor activities in subjects on high and regular sodium diets, [Sar, Ile]-AII being more potent than [Sar, Ala]-AII. Both AIIA caused similar elevation of PAC in subjects on high and regular sodium diets, and an equally fall in PAC in subjects on a low sodium diet. Both AIIA strongly antagonized the rise in BP, the increase in PAC and the reduction of Ccr induced by AII administration in subjects on all three sodium diets. The results indicate that both AIIA can be used to examine the activity of the renin-angiotensin system in patients with hypertension, and they also suggest that AII interaction with its receptors differs in different target tissues.
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PMID:Effects of two angiotensin II analogues on blood pressure, plasma aldosterone concentration, plasma renin activity and creatinine clearance in normal subjects on different sodium intakes. 700 66

The components of the renin-angiotensin system have been implicated in the development of primary hypertension in humans and genetically hypertensive rats. In humans a mutation in the angiotensinogen gene and elevated plasma angiotensinogen levels have been linked to primary hypertension. Although we had previously excluded a linkage of blood pressure to the angiotensinogen gene in the stroke-prone spontaneously hypertensive rat (SHRSP), elevated angiotensin II (Ang II) levels in this strain compared with the normotensive reference, the Wistar-Kyoto rat (WKY), prompted us to investigate further into the origins and effects of altered Ang II regulation using a range of physiological, biochemical, molecular, and genetic approaches. Ang II plasma levels determined by radioimmunoassay were confirmed to be significantly elevated in SHRSP compared with WKY. Sequence comparison among the two rat strains revealed a mutation in the coding region of the angiotensinogen gene that results in an isoleucine-to-valine substitution in SHRSP at amino acid position 154 (I154V). We performed a cosegregation analysis in an F2 intercross cohort bred from SHRSP and WKY from the University of Heidelberg (SHRSPHD and WKYHD) to address the following questions: (1) whether this or another mutation of the angiotensinogen gene may be casually related to the observed differential Ang II plasma levels, (2) whether Ang II plasma levels may be correlated with blood pressure or organ hypertrophy, and (3) whether genetic linkage to the renin or angiotensin-converting enzyme (ACE) gene loci (the two classic regulatory enzymes of the renin-angiotensin system) may provide an explanation for elevated Ang II plasma levels.(ABSTRACT TRUNCATED AT 250 WORDS)
Hypertension 1995 Aug
PMID:Altered angiotensinogen amino acid sequence and plasma angiotensin II levels in genetically hypertensive rats. A study on cause and effect. 763 35

Generalized glucocorticoid resistance is associated with chronic hyperactivation of the hypothalamic-pituitary-adrenal axis, compensating for impaired glucocorticoid receptor function. We report a unique patient with sporadic generalized glucocorticoid resistance who, at age 33, presented with infertility and hypertension and, at 38, developed pituitary Cushing's disease. Leukocyte-binding studies revealed normal affinity of the glucocorticoid receptor but a reduction of binding sites by 50%. [3H]thymidine incorporation by this patient's lymphocytes was not suppressible by dexamethasone. He had a novel heterozygous missense mutation in the glucocorticoid receptor gene (isoleucine 559 to asparagine 559). The mutant receptor exhibited a strong dominant-negative effect on the ability of the wild-type receptor to induce gene transcription in vitro. The mutation was present in all of the patient's cultured lymphoblasts and fibroblasts as well as in 50% of his sperm, as demonstrated by single-cell polymerase chain reaction; it was not present in his parents and seven siblings. This novel mutation was thus both de novo and present in the germ line. Immunohistochemical staining of this patient's pituitary corticotropinoma revealed accumulation of p53 protein, indicating the presence of a putative somatic oncogenic mutation in the p53 gene in the tumor cells. Investigation of the lymphoblast and skin fibroblast cultures for p53 abnormalities did not show any aberration. Thus, a novel de novo germ line mutation of the glucocorticoid receptor with strong dominant-negative activity caused severe sporadic generalized glucocorticoid resistance, which preceded corticotroph adenoma formation. The latter probably was due to the combined effects of chronic corticotroph hyperstimulation, decreased glucocorticoid negative feedback, and at least one subsequent somatic defect in the control of the cell cycle.
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PMID:Cushing's disease preceded by generalized glucocorticoid resistance: clinical consequences of a novel, dominant-negative glucocorticoid receptor mutation. 886 43

Brain edema sufficient to cause intracranial hypertension and brain herniation remains a major cause of mortality in acute liver failure (ALF). Studies in experimental animal models of ALF suggest a role for ammonia in the pathogenesis of both encephalopathy and brain edema in this condition. As part of a series of studies to evaluate the therapeutic efficacy of ammonia-lowering agents, groups of rats with ALF caused by hepatic devascularization were treated with L-ornithine-L-aspartate (OA), an agent shown previously to be effective in reducing blood ammonia concentrations in both experimental and human chronic liver failure. Treatment of rats in ALF with infusions of OA (0.33 g/kg/h, intravenously) resulted in normalization of plasma ammonia concentrations and in a significant delay in onset of severe encephalopathy. More importantly, brain water content was significantly reduced in OA-treated rats with ALF. These protective effects of OA were accompanied by increased plasma concentrations of several amino acids including glutamate, gamma-aminobutyric acid (GABA), taurine, and alanine, as well as the branched-chain amino acids, leucine, isoleucine, and valine. Increased availability of glutamate following OA treatment provides the substrate for the major ammonia-removal mechanism (glutamine synthetase). Plasma (but not cerebrospinal fluid) glutamine concentrations were increased 2-fold (P <.02) in OA-treated rats, consistent with increased muscle glutamine synthesis. Direct measurement of glutamine synthetase activities revealed a 2-fold increase following OA treatment. These findings demonstrate a significant ammonia-lowering effect of OA together with a protective effect on the development of encephalopathy and brain edema in this model of ALF.
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PMID:L-ornithine-L-aspartate lowers plasma and cerebrospinal fluid ammonia and prevents brain edema in rats with acute liver failure. 1046 68

The Dahl/Rapp rat model of hypertension is characterized by a marked increase in blood pressure and a progressive fall in glomerular filtration rate when salt-sensitive (S) rats are placed on an 8% NaCl diet. On the same diet, the salt-resistant (R) rat does not exhibit these changes. In previous studies we found that protein kinase C (PKC) upregulates Na(+)/Ca(2+) exchanger activity in afferent arterioles and mesangial cells from R but not S rats. One possible reason for the difference in PKC sensitivity may be due to differences in the S and R Na(+)/Ca(2+) exchanger protein. We now report the cloning of Na(+)/Ca(2+) exchangers from R (RNCX1) and S (SNCX1) mesangial cells. At the amino acid level, SNCX1 differs from RNCX1 at position 218 in the NH(2)-terminal domain where it is isoleucine in RNCX1 but phenylalanine in SNCX1. These two exchangers also differ by 23 amino acids at the alternative splice site within the cytosolic domain. RNCX1 and SNCX1 were expressed in OK-PTH cells and (45)Ca(2+)-uptake studies were performed. Acute phorbol 12-myristate 13-acetate (PMA) treatment (300 nM, 20 min) upregulated exchanger activity in cells expressing RNCX1 but failed to stimulate exchanger activity in SNCX1 expressing cells. Upregulation of RNCX1 could be prevented by prior 24-h pretreatment with PMA, which downregulates PKC. These results demonstrate a difference in PKC-Na(+)/Ca(2+) exchange activity between the isoform of the exchanger cloned from the R vs. the S rat. Lack of PKC activation of SNCX1 may contribute to a dysregulation of intracellular Ca(2+) concentration and enhanced renal vasoreactivity in this model of hypertension.
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PMID:Cloning of mesangial cell Na(+)/Ca(2+) exchangers from Dahl/Rapp salt-sensitive/resistant rats. 1089

Essential hypertension has a familial predisposition, but the phenotype of elevated blood pressure has delayed penetrance. Because the kidney is a crucial determinant of blood pressure homeostasis, we studied early glomerular alterations in still-normotensive young subjects at genetic risk of hypertension. Thirty-nine normotensive adults (mean age 29 to 31 years), stratified by genetic risk (parental family history [FH]) of hypertension (26 with positive FH [FH+], 13 with negative FH [FH-]), underwent intravenous infusion of mixed amino acids. Before and during amino acid administration, we measured glomerular filtration rate (GFR), putative second messengers of amino acids (nitric oxide [NO.] metabolites and cGMP), serum insulin and amino acid concentrations, and the FE(Li)+ as an index of renal proximal tubular reabsorption. The FH+ group had a blunted GFR rise in response to amino acids (2.43+/-8.16% versus 31.0+/-13.4% rise, P:=0.0126). The amino acid-induced change in GFR correlated (r=0.786, P:<0.01) with the change in urinary NO. metabolite excretion; a diminished rise in urinary NO. metabolite excretion in the FH+ group (P:=0.0105) suggested a biochemical mechanism for the different GFR responses between FH groups: a relative inability to convert arginine to NO. The FH+ group had a far lower initial cGMP excretion at baseline (261+/-21.1 versus 579+/-84.9 nmol. h(-1)/1.73 m(2), P:=0.001), although cGMP did not change during the amino acid infusion (P:=0.703). FH status, baseline GFR, and baseline serum insulin jointly predicted GFR response to amino acids (P:=0.0013), accounting for approximately 45% of the variance in GFR response. Decline in FE(Li)+, an inverse index of proximal tubular reabsorption, paralleled increase in GFR (r=-0.506, P:=0.01), suggesting differences in proximal tubular reabsorption during amino acids between the FH groups. GFR response to amino acid infusion was blunted in the FH+ group despite significantly higher serum concentrations of 6 amino acids (arginine, isoleucine, leucine, methionine, phenylalanine, and valine) in the FH+ group, suggesting a novel form of insulin resistance (to the amino acid-translocating action of insulin) in FH+ subjects. We conclude that blunted glomerular filtration reserve in response to amino acids is an early-penetrance phenotype seen even in still-normotensive subjects at genetic risk of hypertension and is linked to impaired formation of NO. in the kidney. Corresponding changes in GFR and fractional excretion of Li(+) suggest that altered proximal tubular reabsorption after amino acids is an early pathophysiologic mechanism. Resistance to the amino acid-translocating actions of insulin may play a role in the biological response to amino acids in this setting. This glomerular reserve phenotype may be useful in genetic studies of renal traits preceding or predisposing to hypertension.
Hypertension 2001 Mar
PMID:Early alteration in glomerular reserve in humans at genetic risk of essential hypertension: mechanisms and consequences. 1124 15

Effect of long-term intake of isoleucine-proline-proline (IPP) and valine-proline-proline (VPP), or a sour milk product containing these peptides on development of hypertension was investigated in spontaneously hypertensive rats (SHR). Six-week-old SHR were given: 1) water (control group), 2) IPP and VPP dissolved in water (peptide group) or 3) sour milk containing IPP and VPP (sour milk group) for 12 weeks. Systolic blood pressure (SBP) was measured by tail-cuff method. Development of hypertension was attenuated in the groups receiving tripeptides or sour milk as compared to the control group. At the end of treatment period, SBP was 176 +/- 1 mmHg in sour milk group, 181 +/- 2 mmHg in peptide group, and 193 +/- 1 mmHg in control group (P < 0.001). After treatment withdrawal, SBP rose gradually reaching the level of control group within four weeks' follow-up. In functional bioassay of ACE inhibitory activity, effect of the tripeptides on angiotensin I or angiotensin II-induced contraction in rat mesenteric arteries was evaluated. IPP inhibited the angiotensin I-induced contraction, whereas the angiotensin II-induced contraction remained unaltered. In conclusion, long-term intake of IPP and VPP, or a sour milk containing these tripeptides attenuated the development of hypertension in SHR. One possible mechanism underlying this effect is ACE inhibition.
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PMID:Long-term intake of milk peptides attenuates development of hypertension in spontaneously hypertensive rats. 1178 70

The effect of long-term intake of two fermented milk products on the development of hypertension was compared in young spontaneously hypertensive rats (SHR). The products contained tripeptides isoleucine-proline-proline (IPP) and valine-proline-proline (VPP), which have been shown to possess angiotensin converting enzyme (ACE) inhibitory activity. Six-week-old SHR were divided into four groups to receive orally ad libitum water, skim milk or two fermented milk poducts (fermented milk A or fermented milk B; the latter is commercially available in Japan with trade name Calpis) for 14 weeks. The calculated intake of IPP was 0.4 mg/d and 0.2 mg/d in the groups receiving fermented milk A and B, respectively, whereas the corresponding amounts for VPP were 0.6 mg/d and 0.3 mg/d. Systolic blood pressure (SBP) was monitored weekly by tail-cuff method. The development of hypertension was significantly attenuated in both groups receiving fermented milk products, whereas skim milk did not affect blood pressure. The effect was detectable after 6 weeks of treatment. At the end of the experiment, the lowest blood pressure level was found in the group receiving fermented milk A: the SBP was 21 mm Hg lower than in the group receiving water and 10 mm Hg lower than in the group receiving fermented milk B. This difference could be explained by larger intake of ACE inhibitory tripeptides in the group receiving fermented milk A as compared with fermented milk B.
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PMID:Effect of long-term intake of milk products on blood pressure in hypertensive rats. 1204 1


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